BIG BEAR LAKE, CALIF. The hunt for a former Los Angeles police officer suspected in three killings entered a fourth day, as officials from the Mexico border area to Las Vegas take precautions for the armed and dangerous fugitive. The hunt appeared to be focused on the snow-covered mountains near Big Bear, Calif., Sunday, a day after the LAPD chief ordered a review of the disciplinary case that led to the fugitive's dismissal and new details emerge of the evidence he left behind.

SWAT teams with air support and bloodhounds fanned out in snow-covered Southern California mountains, searching for 33-year-old Christopher Dorner, who has vowed revenge against several former LAPD colleagues whom he blames for ending his career. Authorities planned a 1 p.m. news conference Sunday in Los Angeles to announce a reward for information leading to his arrest.

Earlier, Police Chief Charlie Beck announced officials will re-examine the allegations by Dorner that his law enforcement career was undone by racist colleagues. While he promised to hear out Dorner if he surrenders, Beck stressed that he was ordering a review of his 2007 case because he takes the allegation of racism in his department seriously.

"I do this not to appease a murderer. I do it to reassure the public that their police department is transparent and fair in all the things we do," the chief said in a statement.

Dorner owns a home in Las Vegas, where assistant Las Vegas Sheriff Greg McCurdy told CBS affiliate KLAS Friday afternoon all Metro Police uniformed officers will be traveling in two person units as a precaution in response to the threat Dorner poses to police officers.

"When you have someone who is highly trained, highly capable, having been a police officer in the past, having prior military experience whose made threats, and you've all read about them in the manifesto, we take this very seriously," McCurdy said.

Henderson Police spokesman Keith Paul said all officers who normally patrol on motorcycle have been placed with cars until further notice. He said uniformed officers are working in pairs as staffing allows.

Earlier this week the manhunt was centered in San Diego and officials have again intensified efforts around the border with Mexico, reports CBS affiliate KFMB in San Diego.

Customs and Border Protection said its agents are assisting in the search for Dorner and some lanes at the border have been shut down.

"CBP is also exercising additional vigilance in southbound inspections in Southern California. As a result, travelers heading southbound into Mexico may experience delays," said the CBP in a statement to KFMB.

Heavily armored officers, armed with rifles, could be seen on Saturday surveying vehicles and drivers at the world's busiest border crossing creating a massive bottleneck.

Authorities suspect Dorner in a series of attacks in Southern California over the past week that left three people dead. Authorities say he has vowed revenge against several former LAPD colleagues whom he blames for ending his career. The killings and threats that Dorner allegedly made in an online rant have led police to provide protection to 50 families, Beck said.

A captain who was named a target in the manifesto posted on Facebook told the Orange County Register he has not stepped outside his house since he learned of the threat.

"From what I've seen of (Dorner's) actions, he feels he can make allegations for injustice and justify killing people and that's not reasonable," said Capt. Phil Tingirides, who chaired a board that stripped Dorner of his badge. "The end never justifies the means."

On Saturday, the scaled-back search party took advantage of a break from stormy weather to look for Dorner in the San Bernardino mountains, about 80 miles northeast of downtown Los Angeles, where his burned-out pickup truck was discovered Thursday.

On "CBS This Morning: Saturday," CBS News senior correspondent John Miller reported that Dorner's abandonment of his truck because of a broken axle has prompted authorities to believe that he has shifted "from being the hunter to the hunted."

It's unknown what supplies Dorner was able to carry into the remote mountains east of Los Angeles, Evans reports.

Investigators have been examining the truck to determine if it broke down or was set ablaze as a diversion. Police say the truck had a broken axle. Investigators are trying to determine whether it was already broken when they found it, or whether it was damaged when it was towed away.

Also, newly released surveillance video showed Dorner tossing several items into a Dumpster behind an auto parts store in National City on Monday.

On Friday night, authorities served a search warrant and collected evidence from a Buena Park storage unit as part of their investigation. Irvine police Lt. Julia Engen wouldn't elaborate on the nature of the evidence or say who had rented the unit.

Earlier Friday, another warrant was served at a La Palma house belonging to Dorner's mother. Officers collected 10 bags of evidence, including five electronic items.

In his online manifesto, Dorner vowed to use "every bit of small arms training, demolition, ordnance and survival training I've been given" to bring "warfare" to the LAPD and its families.

Dorner served in the Navy, earning a rifle marksman ribbon and a pistol expert medal. He was assigned to a naval undersea warfare unit and various aviation training units, according to military records. He took leave from the LAPD for a six-month deployment to Bahrain in 2006 and 2007.

The flight training that he received in the Navy prompted the Transportation Security Administration to issue an alert, warning the general aviation community to be on the lookout for Dorner. The extent of his potential flying skills wasn't known, the bulletin said.

Feb. 1 was his last day with the Navy and also the day CNN's Anderson Cooper received a package that contained a note on it that read, in part, "I never lied." A coin riddled with bullet holes that former Chief William Bratton gave out as a souvenir was also in the package.

Police said it was a sign of planning by Dorner before the killing began.

On "CBS This Morning" Friday, Bratton described Dorner as "an incredibly dangerous individual" and reacted to the damaged coin.

"When you see that that coin that was given in friendship and respect has three bullet holes, it's certainly very chilling," Bratton said.

On Feb. 3, police say Dorner shot and killed a couple in a parking garage at their condominium in Irvine. The woman was the daughter of a retired police captain who had represented Dorner in the disciplinary proceedings that led to his firing.

Dorner wrote in his manifesto that he believed the retired captain had represented the interests of the department over his.

Hours after authorities identified Dorner as a suspect in the double murder, police believe Dorner shot and grazed an LAPD officer in Corona and then used a rifle to ambush two Riverside police officers early Thursday, killing one and seriously wounding the other.

The crime spree spanned across a wide swath of Southern California, prompting several police agencies, including the FBI and US Marshall Service, to form a joint investigative task force.

Online Public Information File

Viewers with disabilities can get assistance accessing this station's FCC Public Inspection File by contacting the station with the information listed below. Questions or concerns relating to the accessibility of the FCC's online public file system should be directed to the FCC at 888-225-5322, 888-835-5322 (TTY), or fccinfo@fcc.gov.